Vessel-sparing Radiotherapy for Localized Prostate Cancer to Preserve Erectile Function: A Single-arm Phase 2 Trial

Abstract

Background: Erectile dysfunction remains the most common side effect from radical treatment of localized prostate cancer. We hypothesized that the use of vessel-sparing radiotherapy, analogous to the functional anatomy approach of nerve-sparing radical prostatectomy (RP), would improve erectile function preservation while maintaining tumor control for men with localized prostate cancer.

Objective: To determine erectile function rates after vessel-sparing radiotherapy.

Design, setting, and participants: Men with localized prostate cancer were enrolled in a phase 2 single-arm trial (NCT02958787) at a single academic center.

Intervention: Patients received vessel-sparing radiotherapy utilizing a planning MRI and MRI-angiogram to delineate and avoid the erectile vasculature.

Outcome measurements and statistical analysis: Both physician- and patient-reported inventories were used to capture erectile function at baseline and at 2 and 5 yr after treatment. Validated model-based comparisons were performed to compare vessel-sparing results to nerve-sparing RP and conventional radiotherapy.

Results and limitations: From 2001 to 2009, 135 men underwent vessel-sparing radiotherapy. After a planned interim analysis, the trial was stopped after meeting the primary endpoint. The median follow-up was 8.7 yr, with a ≥94% response rate to all inventories at each time point. At 5 yr, 88% of patients were sexually active with or without the use of sexual aids. The 2-yr erectile function rates were significantly improved with vessel-sparing radiotherapy (78%, 95% confidence interval [CI] 71-85%) compared to modeled rates for convention radiotherapy (42%, 95% CI 38-45%; p<0.001) or nerve-sparing prostatectomy (24%, 95% CI 22-27%; p<0.001). At 2 yr after treatment, 87% of baseline-potent men retained erections suitable for intercourse. The 5- and 10-yr rates of biochemical relapse-free survival were 99.3% and 89.9%, and at 5 yr the biochemical failures were limited to the National Comprehensive Cancer Network high-risk group. The single-arm design is a limitation.

Conclusions: Vessel-sparing radiotherapy appears to more effectively preserve erectile function when compared to historical series and model-predicted outcomes following nerve-sparing RP or conventional radiotherapy, with maintenance of tumor control. This approach warrants independent validation.

Patient summary: In this interim analysis we looked at using a novel approach to spare critical erectile structures to preserve erectile function after prostate cancer radiotherapy. We found that almost 90% of patients at 5 yr after treatment remained sexually active, significantly higher than previous studies with surgery or radiotherapy.

Keywords: Erectile dysfunction; Prostate cancer; Radiotherapy; Vessel-sparing radiation.